Method of noisy signal analysis and apparatus thereof

ABSTRACT

A noisy signal analysis in which a threshold value is set to evaluate the presentation of the display device. The analysis can produce the range of noise level of the image for measuring the distortion block of image caused by the display devices. Furthermore, the apparatus includes a step function generator for producing step functions, a transforming unit for changing threshold value in step functions, and a display for showing the image corresponding to both the high value and low value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus of noisysignal analysis, and more especially, to a method and an apparatus ofnoisy signal analysis applied to the liquid crystal display (LCD).

2. Background of the Related Art

Currently, since the liquid crystal display (LCD) is booming in ITindustry, the monitors of PC have shifted from CRT to the LCD, moreover,the price of LCD is declining very quickly than expected. Although theLCD has a big screen advantage in flat shape, some disadvantages stillexist, for example, color temperature, visible angle, contrast, responsetime and so on.

The LCD manufacturing processes include: array, cell, and assembly, allthese processes encounter many component and assemblies. At endproducts, the test and adjustment are needed due to low stability ofprocesses, the test includes gray test, brightness test, then theelectrical adjustment for characteristic, sometimes, the screen displayshave noisy signal unseen from human eyes, such as flicker.

SUMMARY OF THE RELATED ART

In order to solve the problems mentioned above, the present inventionprovides a method of noisy signal analysis applied to a liquid crystaldisplay. The method adjusts a threshold in a step function and obtains anoisy signal range, which may provide the information to tune the grayvalue and brightness for the LCD.

In order to solve the problems mentioned above, the present inventionprovides an apparatus of noisy signal analysis applied to a liquidcrystal display. The apparatus adjusts the gray value and brightness forthe LCD to observe the noisy range, and provides test person to measurethe LCD quality.

Accordingly, one embodiment of the present invention provides a methodof noisy signal analysis, including: setting a predetermined stepfunction, which changes each signal in a signal group to a firstidentical value; changing a threshold value of the predetermined stepfunction to a first threshold value which induces a first step function,wherein the first step function changes a signal in the signal groupfrom becoming the first identical value to becoming a second identicalvalue; and continuing changing the first threshold value of the firststep function to a second threshold value which induces a second stepfunction, wherein the second step function changes all signals in thesignal group from becoming the first identical value to becoming thesecond identical value.

Additionally, another embodiment of the present invention provides amethod of noisy signal analysis, including: setting a first stepfunction having a first threshold value, and the first step functionchanges each signal in a signal group to a first identical value,wherein the first threshold value changes a specified quantity causingthe first signal in the signal group from becoming the first identicalvalue to becoming the second identical; and setting a second stepfunction having a second threshold value, and the second step functionchanges each signal in a signal group to a second identical value,wherein the second threshold value changes the specified quantitycausing the second signal in the signal group from becoming the secondidentical value to becoming the first identical value; wherein thesignal group has noisy distribution between the first threshold valueand the second threshold value.

Furthermore, another embodiment of the present invention provides anapparatus of noisy signal analysis, including: a step function generatorgenerating a plural step functions, which comprises a first stepfunction having a first threshold value and a second step functionhaving a second threshold value; a transforming unit changing eachsignal in a signal group to a first identical value according to thefirst step function and changing every signal of the signal group to thesecond identical value according to the second step function, whereinthe first threshold value changes a specified quantity causing the firstsignal in the signal group from becoming the first identical value tobecoming the second identical, and the second threshold value changesthe specified quantity causing the second signal in the signal groupfrom becoming the second identical value to becoming the first identicalvalue; and a display device outputting a range of noisy distributionaccording to the first threshold value and the second threshold value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of the apparatus of noisy signal analysisin accordance with an embodiment of the present invention.

FIG. 2 is a flow chart of the method of noisy signal analysis inaccordance with an embodiment of the present invention.

FIG. 3 is another flow chart of the method of noisy signal analysis inaccordance with an embodiment of the present invention.

FIG. 4 illustrates the original image curve displayed on the LCD.

FIG. 5 illustrates the gamma curve of FIG. 4 in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A method and an apparatus of noisy signal analysis are disclosed. Theinvention uses a threshold value in a predetermined step function totest signal appearance in an image displayed on a screen of Flat PanelDisplay (FPD), whereupon, a noisy distribution will be obtained fornoisy signal analysis for that FPD.

FIG. 1 is a functional diagram of the apparatus of noisy signal analysisin accordance with an embodiment of the present invention. The apparatusof noisy signal analysis includes: a step function generator 12generates a plural step functions according to a gamma correctionfunction. The step function generator 12 includes a first step functionhaving a first threshold value and a second step function having asecond threshold value; a transforming unit 14 changes each signal in asignal group to a first identical value according to first step functionand every signal of the signal group to the second identical valueaccording to the second step function. The first threshold value changesa specified quantity causing the first signal in the signal group frombecoming the first identical value to becoming the second identical, andthe second threshold value changes the specified quantity causing thesecond signal in the signal group from becoming the second identicalvalue to becoming the first identical value; and a display device 16outputs a range of noisy distribution according to the first thresholdvalue and the second threshold value.

Accordingly, The first identical value is greater than the secondidentical value, and the first threshold value is smaller than thesecond threshold value. The way of changing the first threshold value isincreased with the specified quantity, and the way of changing thesecond threshold value is decreased with the specified quantity.

In another embodiment, the first identical value is smaller than thesecond identical value, and the first threshold value is greater thanthe second threshold value. The way of changing the first thresholdvalue is decreased with the specified quantity, and the way of changingthe second threshold value is increased with the specified quantity.

Additionally, the display device 16 may be a flat panel display (FPD) ora liquid crystal display (LCD).

FIG. 2 is a flow chart of the method of noisy signal analysis inaccordance with an embodiment of the present invention. The method ofnoisy signal analysis includes following steps: in step S10 setting apredetermined step function. Two identical values, a high value (HVAL)and a low value (LVAL) of gray level on a image signal of the displaydevice are set up. The HVAL is greater than LVAL, and the predeterminedstep function changes each signal value in the group of image signal tothe HVAL; In step S11 setting a threshold value in the predeterminedstep function to induce a first step function, the threshold value ofthe predetermined step function is increased to a first threshold valuewhich induces a first step function, wherein the first step functionchanges a signal value in the signal group from becoming the HVAL tobecoming the LVAL. The first threshold value is the lower bound of theimage signal; in step S12 setting a threshold value in the first stepfunction to induce another step function, the first threshold value instep S11 is continually increased to a second threshold value whichinduces a second step function, wherein the second step function changesall signal in signal group from becoming the HVAL to becoming the LVAL.The second threshold value is the upper bound of the image block and isgreater than the first threshold value; in step S13 obtaining a noisysignal range, a range between the upper bound and the lower bound isobtained for noisy signal range of the image on display device.

Furthermore, changing the threshold value causing the signal in theimage signal from LVAL to HVAL using the flowchart of FIG. 2 is anothermethod of noisy signal analysis in accordance with an embodiment of thepresent invention. The method of noisy signal analysis includesfollowing steps: in step S10 establishing a predetermined step function.Two identical values, a low value (LVAL) and a high value (HVAL) of graylevel on a image signal of the display device are set up. The HVAL isgreater than LVAL, and the predetermined step function changes eachsignal value in the group of image signal to the LVAL; in step S11setting a threshold value in the predetermined step function to induce afirst step function, the threshold value of the predetermined stepfunction is decreased to a first threshold value which induces a firststep function, wherein the first step function changes a signal value inthe signal group from becoming the LVAL to becoming the HVAL. The firstthreshold value is the upper bound of the image signal; in step S12setting a threshold value in the step function to induce another stepfunction, the first threshold value in step S11 is continually decreasedto a second threshold value which induces a second step function,wherein the second step function changes all signal in signal group frombecoming the LVAL to becoming the HVAL. The second threshold value isthe lower bound of the image block and is smaller than first thresholdvalue; in step S13 obtaining a noisy signal range, a range between theupper bound and the lower bound is obtained for noisy signal correctionof the image on display device.

Additionally, the display device may be a flat panel display (FPD) or aliquid crystal display (LCD).

FIG. 3 is a flow chart of the method of noisy signal analysis inaccordance with another embodiment of the present invention. The methodof noisy signal analysis includes following steps: S20 setting a firststep function having a first threshold value, and the first stepfunction changes each signal in a signal group to a first identicalvalue, wherein the first threshold value changes a specified quantitycausing the first signal in the signal group from becoming the firstidentical value to becoming the second identical; and S21 setting asecond step function having a second threshold value, and the secondstep function changes each signal in a signal group to a secondidentical value, wherein the second threshold value changes thespecified quantity causing the second signal in the signal group frombecoming the second identical value to becoming the first identicalvalue; wherein the signal group has noisy distribution between the firstthreshold value and the second threshold value.

Accordingly, first identical value is greater than second identicalvalue, and the first threshold value is smaller than the secondthreshold value. The way of changing the first threshold value isincreased with the specified quantity, and the way of changing thesecond threshold value is decreased with the specified quantity. Inanother embodiment, first identical value is smaller than secondidentical value, and the first threshold value is greater than thesecond threshold value. The way of changing the first threshold value isdecreased with the specified quantity, and the way of changing thesecond threshold value is increased with the specified quantity.

Accordingly, the gamma correction function may be used as the stepfunction in the invention. FIG. 4 illustrates the original image curve30 displayed on the LCD. In applying the invention, the FIG. 5illustrates the gamma curve of FIG. 4 in accordance with an embodimentof the present invention. Firstly, setting HVAL 41 and LVAL 42;secondly, setting a threshold value and increasing threshold valve untillower bound (LB) 43 value displayed in the image block; next,continually increasing the threshold value until all image block displayupper bound (UB) 44 value; finally, the range between lower bound valueand upper bound value is used for gray noisy signal in display device.

Furthermore, the invention is not limited to the gamma correctionfunction, further the Look Up Table (LUT), polynomial function, andpiecewise interpolation may be used and make the present inventiondisplays noisy signal effectively for checking the defects of thedisplay device.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that other modificationsand variation can be made without departing the spirit and scope of theinvention as hereafter claimed.

1. A method of noisy signal analysis, comprising: (a) setting apredetermined step function, wherein said predetermined step functionchanges each signal in a signal group to a first identical value; (b)changing a threshold value of said predetermined step function to afirst threshold value which induces a first step function, wherein saidfirst step function changes a signal in said signal group from becomingsaid first identical value to becoming a second identical value; and (c)continuing changing said first threshold value of said first stepfunction to a second threshold value which induces a second stepfunction, wherein said second step function changes all signals in saidsignal group from becoming said first identical value to becoming saidsecond identical value.
 2. The method of noisy signal analysis accordingto claim 1, wherein said signal group has noisy distribution betweensaid first threshold value and said second threshold value.
 3. Themethod of noisy signal analysis according to claim 2, wherein said firstidentical value is greater than second identical value, and said firstthreshold value is smaller than said second threshold value.
 4. Themethod of noisy signal analysis according to claim 3, in step (b) theway of changing said threshold value is to increase said threshold valueto said first threshold value.
 5. The method of noisy signal analysisaccording to claim 3, in step (c) the way of changing said firstthreshold value is to increase said first threshold value to said secondthreshold value.
 6. The method of noisy signal analysis according toclaim 2, wherein said first identical value is smaller than secondidentical value, and said first threshold value is greater than saidsecond threshold value.
 7. The method of noisy signal analysis accordingto claim 6, in step (b) the way of changing said threshold value is todecrease said threshold value to said first threshold value.
 8. Themethod of noisy signal analysis according to claim 6, in step (c) theway of changing said first threshold value is to decrease said firstthreshold value to said second threshold value.
 9. The method of noisysignal analysis according to claim 2, wherein said signal group is thepixels of one image.
 10. The method of noisy signal analysis accordingto claim 9, wherein said image signal is outputted from a displaydevice, and each signal from said signal group corresponding to saidfirst identical value or said second identical value after beingtransformed.
 11. The method of noisy signal analysis according to claim9, wherein said predetermined step function is generated by adjusting agamma correction function.
 12. An apparatus of noisy signal analysis,comprising: a step function generator generating a plural stepfunctions, wherein said plural step functions comprises a first stepfunction having a first threshold value and a second step functionhaving a second threshold value; a transforming unit changing eachsignal in a signal group to a first identical value according to saidfirst step function and changing every signal of said signal group tosaid second identical value according to said second step function,wherein said first threshold value changes a specified quantity causingthe first signal in said signal group from becoming said first identicalvalue to becoming said second identical, and said second threshold valuechanges said specified quantity causing the second signal in said signalgroup from becoming said second identical value to becoming said firstidentical value; and a display device outputting a range of noisydistribution according to said first threshold value and said secondthreshold value.
 13. The apparatus of noisy signal analysis according toclaim 13, wherein said first identical value is greater than said secondidentical value, and said first threshold value is smaller than saidsecond threshold value.
 14. The apparatus of noisy signal analysisaccording to claim 13, the way of changing said first threshold value isincreased with said specified quantity, and the way of changing saidsecond threshold value is decreased with said specified quantity. 15.The apparatus of noisy signal analysis according to claim 12, whereinsaid first identical value is smaller than said second identical value,and said first threshold value is greater than said second thresholdvalue.
 16. The apparatus of noisy signal analysis according to claim 15,the way of changing said first threshold value is decreased with saidspecified quantity, and the way of changing said second threshold valueis increased with said specified quantity.
 17. The method of noisysignal analysis according to claim 12, wherein said step functiongenerator generating a plural step functions according to a gammacorrection function.
 18. A method of noisy signal analysis, comprising:(a) setting a first step function having a first threshold value, andsaid first step function changes each signal in a signal group to afirst identical value, wherein said first threshold value changes aspecified quantity causing the first signal in said signal group frombecoming said first identical value to becoming said second identical;and (b) setting a second step function having a second threshold value,and said second step function changes each signal in a signal group to asecond identical value, wherein said second threshold value changes saidspecified quantity causing the second signal in said signal group frombecoming said second identical value to becoming said first identicalvalue; wherein said signal group has noisy distribution between saidfirst threshold value and said second threshold value.
 19. The method ofnoisy signal analysis according to claim 18, wherein said firstidentical value is greater than second identical value, and said firstthreshold value is smaller than said second threshold value.
 20. Themethod of noisy signal analysis according to claim 19, wherein the wayof changing said first threshold value is increased with said specifiedquantity, and the way of changing said second threshold value isdecreased with said specified quantity.
 21. The method of noisy signalanalysis according to claim 18, wherein said first identical value issmaller than second identical value, and said first threshold value isgreater than said second threshold value.
 22. The method of noisy signalanalysis according to claim 21,wherein the way of changing said firstthreshold value is decreased with said specified quantity, and the wayof changing said second threshold value is increased with said specifiedquantity.
 23. The method of noisy signal analysis according to claim 18,wherein said first step function and said second step function aregenerated by a gamma correction function.